Safety electric control device



July 3, 1928.

l. E. M CABE SAFETY ELECTRIC CONTROL DEVICE Fil 1 1925 5 Sheets-Sheet lINVENTOR I By ZEM CZBE A TTORNEY July 3, 1928. 1,675,897

I. E. M CABE SAFETY ELECTRIC CONTROL DEVICE Filed June 4, 1925 aShets-Sheet 2 Fig.2

[N VENTOR 'A TTORNEY July'3, 1928. I 1,675,897

I. E. MGCABE SAFETY ELECTRIC CONTROL DEVICE Filed June 4,1925 I:Sheets-Sheet 3 15'. Means Efl m ATTORNEY ratented July 3, 1928. v

IRA E. HGCABE, OI CHICAGO, ILLINOIS.

SAFETY ELECTRIC CONTROL DEVICE.

Application filed June 4, 1925. Serial No. 34,794.

This invention relates to improvements in electric circuit controls andmore particularly to an improved safety device for circuit controls.

It is an object of this invention to provide a device of this characterfor electric stack arising from the fire pot operates a.

thermostat to close the circuit to the motor operating the burnermechanism. lVhile this is one of the preferred uses of this safetydevice, the invention is not limited to this use alone. as the principleof this safety device may be applied to other forms of electric circuitcontrols. where a positive operating safety device is desired which doesnot depend upon elements that are subject to deterioration or loss ofoperating power.

In the drawings:

Figure 1 a top'plan view of an embodiment of this invention in a stackcontrol. with parts broken away.

Figure 2 is a view in side elevation of Figure l. partly injsection andwith parts broken away.

Figure 3 is a view in front elevation with the cover of the casingremoved and the electric circuit shown in diagram.

In this particular embodiment of this invention. the control mechanismis contained within a circular casing 1 secured to one end of a sleeve 2surrounding one form of a thermostatic stack control element 3 whichprojects'through the other end of the sleeve and is adapted to enterwithin the walls 4 of a stack leading from the fire pot of anelectrically operated domestic oil burner heater or hot air duct. notshown. and to which the adjacent end of the sleeve 2. is secured, asillustrated in Figure 1. The thermostatic element 3, as illustrated,comprises a tube of resilient metal, preferably containing a thermalfluid, which enters the stack in the form of a loop with one end portionwithin the sleeve 2 formed into a coil 5 having the free end of the coiladjacent to the casing provided with a prowhich in turn will be jection6 entering the interior of the casin through an aperture providedtherefor. t is readily seen that when the stack is cool the coil 5willb'e in its normal or contracted position with the projection 6 atone end of its movement and as the stack becomes filled with heated airand gases which pass about the loop of the thermostatic element 3extending into their path the increase in temperature will betransmitted to the coil caused to expand or uncoil in the nature of apressure or Bourdon tube thereby causing the projection 6 of the end ofthe coil to travel as the arc of a circle towards the other end of ,itsmovement. This movement operates the control switch, or any other typeof thermostatic element having a moving part could be employed as wellto operate the control switch.

The controlswitch is mounted on a plate 7 pivoted at one end upon ashaft secured thereto mounted to rotate in bearings on two plates 8 and9 carried upon the rear wall of the casing below the aperture 10 thereinthrough which the pro ection 6 of the thermostatic element enters. Thecontrol switch as illustrated comprises a mercury switch tube, 11, withboth terminals entering the end adjacent the pivot, mounted upon arectangular bracket extending from plate 7 and having a counter weight12 under the end farthest from the pivot so that when acted upon by thecounter weight the tube will be tilted so that the mercury will assemblein that end and break the circuit and when tilted beyond the horizontalin the other direction the mercury will assemble about the terminalsentering therein and close the circuit. Movement of the projection 6 ofthethermostatic element is transmitted to the tilting mercury tubeswitch 11 by means of a forked link 13 embracing the projection 6 andfrictionally engaged to a. boss 14 upon the pivot shaft of plate 7. bysplitting the link from the boss to the lower end and engaging the splitportions by a set screw. The plate 7 preferably is provided with twospaced apart projections 15 arranged to en gage on either side of one ofthe studs 16 spacing apart plates 8 and 9 and limit the tilting of theplate 7 and mercury tube switch 11 in both directions. The tilting link13 is provided with-a frictional engagement with the pivot shaft ofplate 7 to allow further expansion or contraction of the coil 5 afterthe forked link has tilted the mere cury tube switch to the limit of itsmovement in either direction, the set screw regulating the frictionclutch to allow of such movement.

The safety device for the thermostatic operated switch 11 comprisesanother mercury switch tube 17 carried on a. plate-18 pivotally mountedupon the back of the till casing 1 with the terminals entering the tubeat the end adjacent the pivot. The free end of the plate 18 is adaptedto engage over a projection 19 upon a pivoted member 20 rotatable abouta pivot 21 thereabove and when so engaged will support the plate 18 withpoints of engagement of free end and pivot in a horizontal plane. Themercury switch tube 17 is mounted upon the plate 18 by clips so arrangedthat when the plate is horizontal and engaged by the pivoted member 20the tube will be tilted so that the mercury will assemble at the endadjacent the plate pivot and close the contact between the terminals. Itis preferable to provide a plate 22 secured to the rear of the casingwhich carries the pivots of the plate 18 and member 20 and extends belowthe plate 18 which will also act as an anchor for a spring therefrom tothe underside of the plate 18 to cause the same to firmly engage theupper side of the projection 19 and also as an anchor for a springtherefrom to the rotatable member 20 to cause it to engage the end ofthe plate 18 and resist disengagement from vibration or jars. The pivot21 of member 20 is so-arranged that when the member hangs normally theprojection thereon will be in line to engage the end of the mercury tubeplate 18 so that an outward movement of the pivoted member will releasethe plate whichwhen freed will drop that end and rotate upon its pivottilting the mercury tube causingthemercury to assemble at that end andbreak the contact between the terminals.

In order to impart an outward movement of the pivoted member to free thetube plate 18 after a predetermined time, a bar of expansible metal 23,is mounted to slide in a bearing 24 upon plate 22 and in an adjustableanchor bearing 25 in the side wall of the casing 1. Three binding postsare arranged on the rear wall of the casing below the bar 23, as shownin Figure 3, one.

of which, 26, is connected exterior of the casing to the commercial lineand on the interior of the casing to one terminal of the mercury switchtube 11- with the other terminal of this switch tube connected to theadjacent binding post 27 and this bindingpost in turn is connected toone termmal' of the mercury switch tube 17 with the other terminal ofthat tube connected to the third binding post 28 which binding post onthe exterior of the casing is conin Figure 3, illustrating a roomthermostat T and boiler control B, customary in oil burner heatingsystems, in circuit with the safety control switch and motor M. Theadjustable anchor bearing of the expansible metal rod 23 is set so thatunder normal conditions the closing of the main commercial circuit byhand, and when so closed by thermostat T and boiler control B, will passthe current through the resistance coil 29 and switch tube 17 asufficient time for the motor to operate the burner mechanism to ignitethe flame and cause the stack control to operate the switch tube 11 toclose the main circuit therethrough before the metal rod is expandedsufficiently to trip the safety switch. Should the burner fiamc fail toignite or from any cause cease while the motor is operating, the stackcontrol will cool and break the circuit through mercury tube 11 and thenthe metal rod will expand and disconnect the pivoted member from thesafety switch plate allowing the same to tilt and break the circuittherethrough and to the motor. When the safety switch has once operatedto break the motor circuit the burner mechanism cannot be started untilit has been reset. To reset the safety switch a plunger 30 is mounted inthe side wall of the casing 1 directly under the pivoted switch carryingplate 18 which not only limits {the downward swing of the of the casingcan beadjusted to regulate the length of the expansible metal rodextending within the casing and thereby the time required, after themotor circuit has been closed while tube switch 11 is open, to expandsufficiently under the heat from coil 29 to trip the safety switch.

It is to be noted that this construction provides a safety device thatmay be operated innumerable times without showing wear or deteriorationand may be depended upon to operate under all conditions. Furthermorethe frictional engagement between the forked link 13 and the rotatablepivot secured to plate 7 carrying the mercury tween the forked link andshaft, thereby device for permitting greater movement than that justnecessary to throw the switch without injuring any part of the mechanismand the counter weight 12 will always return the switch to open positionas soon as the actuating member 6 moves in the opposite direction andthen the frictional engagement will permit the member to resume itsnormal position. The, frictional engagement between these parts not onlycompensates for movement greater than that necessary to throw the switchin both directions but also in connection with the weight of the switchand counter weight provides an additional safety should at any time orfor any reason or in any position of the switch the frictionalengagement between these two parts become insufficient' to operate theswitch,-the switchwill be at once tilted to the open position and breakthe circuit. This device therefore contains two safety elements, namely,the time controlled electrically operated lower switch mechanism and thefrictional compensating and safety connection between the upper switchand its operating mechanism.

at I claim is:

1. A safety electrical control device including a thermostaticallycontrolled electric switch, an additional switch normally in circuitbetween said first switch and the main circuit, and a time elementbetween the poles of the first switch completing the main circuit to thesecond switch for breaking the circuit through the second switch,whereby the closing of the main circuit when the first switch is in V ofthermostatlcally controlled switch to close 0 en position will, uponfailure within a predetermined time, break the main circuit through thesecond switch.

2. Asafety electric control device comprising a thermostaticallyactuated switch and a gravity actuated switch in series therewith, meansfor detachably maintaining the second switch in circuit, and meansoperable upon closing the main circuit to release the gravity actuatedswitch to break the main circuit upon failure of the thermostaticallyactuated switch to close the main circuit therethrough.

3. A safety electric control device including a thermostaticallyactuated switch in the main circuit having an additional and gravityactuated switch in series therewith and the main circuit, a shuntcircuit between the poles of the first switch, means for'detachablyholding the gravity actuated switch in closed position and meansactuated by the shunt circuit to release the second switch to beactuated by gravity to brealcthe main circuit upon failure of the firstswitch to maintain the main circuit closed therethrough.

4. A safety electric control device including thermostatically actuatedand gravity actuated switches. in series with each other and the maincircuit, a shunt circuit between the poles of the first switch,detachable means .for holding the second switch in closed positionagainst the force of gravity. adjustable means actuated by the shuntcircuit, upon failure of the first switch to close a predet-ermined timeafter the closing of the main circuit, to release the second switch andallow gravity to break the main circuit therethrough. y

5. A safety electric control device having a thermostatically actuatedswitch, normally open, and a gravity actuated switch, having means'formanually closing the same, connected in series with each other and themain circuit, means for detachably engaging the gravity switch whenmanually closed, and electrically actuated means in circuit with thefirst switch actuated by the closure of the main circuit, upon failureof the thermostatically actuated switch to close said circuittherethrough, to release the engagement of the second switch, whereupongravity actuates the second switch tobreak the main circuit therethroughand through the electrically actuated means.

' 6. A safety electric control device including an automaticallycontrolled switch with a safety switch connected in series therewithcomprising a mercury switch tube having terminals adjacent one end androtatable about a pivot adjacent that end. releasable means normallymaintaining the tube in posit-ion to close the circuit through itsterminals, and means operable upon closing the open positions, a secondtilting mercury on the casing, detach-' tube switch mounted able meansnormally maintaining the second switch in closed position, one terminalof each switch connected to each other with the other terminals adaptedto be connected with the main circuit, a shunt circuit between the polesof the first switch adapted to actuate means for releasing the secondswitch upon closlng the main clrcuit exterior of the casing upon failureof the first switch within a predetermined time thereafter to close themain circuit therethrough, and means to tilt the released second switchto break the main circuit therethrough.

8. A safety electric control device comprising a casing, two tiltingmercury tube switches mounted therein in series with each other andadapted to be placed in series with the main circuit, means upon bothswitches for tilting them to the open position, means exterior of thecasing for automatically tilting one switch to its closed position,means passing through the casing for manually tilting the other switchto closed position, mechanical means adapted to releasably engage andhold the manually tilted switch in closed position, electricallyactuated means within the casing for releasing the manually tiltedswitch to break the circuit, means connecting said last named mean 'n ashunt circuit between the poles of the 0 her switch, whereby the closingof the mairr circuit without the casing causes said electricallyactuated means to release he second switch upon failure of the automaticmeans to tilt the first switch to closed position.

9. In a device of the character described,

a casing, two mercury tube switches having terminals adjacent one endmounted upon brackets turning upon pivots adjacent their terminals uponthe casing, whereby they both will assume'the open position, oneterminal of each switch having a flexible connection to a terminal ofthe other and the other terminals of each switch having a flexibleconnection to atbinding post upon the casing adapted to connect saidswitches in series with an exterior main circuit, said wall of thecasing having an aperture provided adjacentthe pivot of one switch foradmitting the entrance of an automatically actuated member adapted toengage the bracket of that switch and when actuated to tilt that switchto closed position, a member pivoted upon the casing above the free endof the bracket of the other switchadapted to engage said bracket andreleasal ly hold the same when its switch is tilted to closed position,an expansible rod mounted within the casing having one end anchored andthe other end adjacent said pivoted member when holding said switch inclosed position, a heat producing coil about said rod connected in shuntcircuit between the poles of the automatically actuated switch, wherebyupon closing the ma circuit exterior of the casing the shunt circuitwill expand the rod to release the switch from the pivoted member tobreak the main circuit in a predetermined time thereafter upon failureof the automatically switch provided with an attachment to the switchpermitting movement of said member beyond that necessary for throwingthe switch in either direction, nonresilient means in connection withthe switch to positively return the switch to open position upon failureof the attachment, and a gravity operated switch in series with thefirst switch normally detachably held in closed position andelectrically actuated means operable upon closing the main circuit aftera predetermined time to release the second switch permitting gravity toturn it to open position upon failure of theautomatically actuated meansto close the first switch.

11. A safety electric control device comprising an automaticallyactuated tilting mercury tube switch, having an operating.

member for tilting said switch with a fric; tional engagement theretoadapted to be engaged by controlling the switch to tilt the switch toopen and closed position and permit movement of the operating membertherebeyond in relation to the switch, a counter weight connected tothemercury switch tube adapted to normally maintain the tube in an openposition and return the tube to that position upon failure of thefrictional engagement with operating member, and a gravity actuatedtilting mercury tube switch in series with the first switch havingreleasable means normally maintaining tsaid tube in the closed position,an expansible rod adapted to release the gravity switch and a heatproducing coil about said rod in a shunt circuit between the poles ofthe first switch, whereby upon closing the main circuit the failureof'the automatically actuated means to close the first switch will causethe rod to expand and release the gravity switch to break the circuit.

IRA E. MQCABE.

the automatically actuated means I V

